To assist with surgical removal of cancerous lesions, surgeons use hand-held guiding instruments such as intra-operative probes. Before surgery, patients are injected with radio-labeled biomarker which is predominantly uptaken by the cancer tissue.
Usually these devices are simple and work on the “Geiger counter” principle i.e. they only measure intensity of the radioactive signal in the vicinity of the probe sensor/tip and provide audio and/or visual feedback to the operator/surgeon (see for example, Ramsey et al., U.S. Pat. No. 4,889,991, Dec. 26, 1989, Denen et al., U.S. Pat. No. 5,151,598, Sep. 29, 1992, and Yarnall et al., U.S. Pat. No. 6,331,703, Dec. 18, 2001). By scanning the probe in front of the tissue and zooming on the region producing the strongest signal, the information on the lesion location is obtained, directly correlated with the anatomical detail, as visually analyzed by the surgeon. This time-consuming procedure suffers generally from poor probe sensitivity and, therefore, poor cancer margin definition.
There have been many attempts to address the issue of providing better, faster and more accurate cancer tissue position information by constructing small imaging probes. These mini-imagers can be for gamma imaging or for positron imaging, or for both. Several companies are producing such probes (for example, Gamma Medica and IntraMedical Imaging and many more designs are described in scientific literature and in patents such as U.S. Pat. No. 6,628,984 by Weinberg, Sep. 30, 2003.
However, all these instruments suffer from a major inconvenience from the surgeon's point of view which is that they locally obstruct the view of the surgical field and do not actually help with the exact location of the tissue to be surgically removed. More accurate and larger image of the scanned region per se but without optical etc co-registration with anatomical detail is deemed not to be that useful by surgeons.
In addition, these mini-imagers are not actually easily “hand-held” because their weight is usually in the range of 1-3 pounds. While mechanical support systems were designed to support the imaging probes in place, these devices further exacerbate the above mentioned viewing field obstruction issue. To remedy the obstruction and weight issues some of the proposed imaging probes are made compact with even smaller field of view, however then their utility as imagers is limited. Another approach is to limit the size of the instrument at the surgical end by installing thereon only a scintillator gamma sensor which is optically connected to a distant position sensitive photodetector via a flexible optical fiberoptic lightguide (Daghighian et al., U.S. Pat. No. 5,325,855, Jul. 5, 1994). However, in this case there are the same issues of visual field obstruction and limited field of view. Flexible light guides usually limit the field of view even more.